/*
  KeePass Password Safe - The Open-Source Password Manager
  Copyright (C) 2003-2017 Dominik Reichl <dominik.reichl@t-online.de>

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Security;
using System.Diagnostics;

#if !KeePassUAP
using System.Security.Cryptography;
#endif

using KeePassLib.Resources;

namespace KeePassLib.Cryptography.Cipher
{
  /// <summary>
  /// Standard AES cipher implementation.
  /// </summary>
  public sealed class StandardAesEngine : ICipherEngine
  {
#if !KeePassUAP
    private const CipherMode m_rCipherMode = CipherMode.CBC;
    private const PaddingMode m_rCipherPadding = PaddingMode.PKCS7;
#endif

    private static PwUuid g_uuidAes = null;

    /// <summary>
    /// UUID of the cipher engine. This ID uniquely identifies the
    /// AES engine. Must not be used by other ciphers.
    /// </summary>
    public static PwUuid AesUuid
    {
      get
      {
        PwUuid pu = g_uuidAes;
        if (pu == null)
        {
          pu = new PwUuid(new byte[] {
                        0x31, 0xC1, 0xF2, 0xE6, 0xBF, 0x71, 0x43, 0x50,
                        0xBE, 0x58, 0x05, 0x21, 0x6A, 0xFC, 0x5A, 0xFF });
          g_uuidAes = pu;
        }

        return pu;
      }
    }

    /// <summary>
    /// Get the UUID of this cipher engine as <c>PwUuid</c> object.
    /// </summary>
    public PwUuid CipherUuid
    {
      get { return StandardAesEngine.AesUuid; }
    }

    /// <summary>
    /// Get a displayable name describing this cipher engine.
    /// </summary>
    public string DisplayName
    {
      get
      {
        return ("AES/Rijndael (" + KLRes.KeyBits.Replace(@"{PARAM}",
            "256") + ", FIPS 197)");
      }
    }

    private static void ValidateArguments(Stream stream, bool bEncrypt, byte[] pbKey, byte[] pbIV)
    {
      Debug.Assert(stream != null); if (stream == null) throw new ArgumentNullException("stream");

      Debug.Assert(pbKey != null); if (pbKey == null) throw new ArgumentNullException("pbKey");
      Debug.Assert(pbKey.Length == 32);
      if (pbKey.Length != 32) throw new ArgumentException("Key must be 256 bits wide!");

      Debug.Assert(pbIV != null); if (pbIV == null) throw new ArgumentNullException("pbIV");
      Debug.Assert(pbIV.Length == 16);
      if (pbIV.Length != 16) throw new ArgumentException("Initialization vector must be 128 bits wide!");

      if (bEncrypt)
      {
        Debug.Assert(stream.CanWrite);
        if (!stream.CanWrite) throw new ArgumentException("Stream must be writable!");
      }
      else // Decrypt
      {
        Debug.Assert(stream.CanRead);
        if (!stream.CanRead) throw new ArgumentException("Encrypted stream must be readable!");
      }
    }

    private static Stream CreateStream(Stream s, bool bEncrypt, byte[] pbKey, byte[] pbIV)
    {
      StandardAesEngine.ValidateArguments(s, bEncrypt, pbKey, pbIV);

      byte[] pbLocalIV = new byte[16];
      Array.Copy(pbIV, pbLocalIV, 16);

      byte[] pbLocalKey = new byte[32];
      Array.Copy(pbKey, pbLocalKey, 32);

#if KeePassUAP
			return StandardAesEngineExt.CreateStream(s, bEncrypt, pbLocalKey, pbLocalIV);
#else
      RijndaelManaged r = new RijndaelManaged();
      if (r.BlockSize != 128) // AES block size
      {
        Debug.Assert(false);
        r.BlockSize = 128;
      }

      r.IV = pbLocalIV;
      r.KeySize = 256;
      r.Key = pbLocalKey;
      r.Mode = m_rCipherMode;
      r.Padding = m_rCipherPadding;

      ICryptoTransform iTransform = (bEncrypt ? r.CreateEncryptor() : r.CreateDecryptor());
      Debug.Assert(iTransform != null);
      if (iTransform == null) throw new SecurityException("Unable to create Rijndael transform!");

      return new CryptoStream(s, iTransform, bEncrypt ? CryptoStreamMode.Write :
          CryptoStreamMode.Read);
#endif
    }

    public Stream EncryptStream(Stream sPlainText, byte[] pbKey, byte[] pbIV)
    {
      return StandardAesEngine.CreateStream(sPlainText, true, pbKey, pbIV);
    }

    public Stream DecryptStream(Stream sEncrypted, byte[] pbKey, byte[] pbIV)
    {
      return StandardAesEngine.CreateStream(sEncrypted, false, pbKey, pbIV);
    }
  }
}
